Storage access coordination using CORBA

We describe our experience with using several CORBA products to interconnect the software modules of a fairly complex storage coordination system. In the application area of High Energy and Nuclear Physics (HENP) the volume of data reaches hundreds of terabytes per year, and therefore it is impractical to store them on disk systems. Rather they are stored on robotic tape systems that are managed by some mass storage system (MSS). The role of the Storage Access Coordination System (STACS) that we developed is to manage the caching of files from the MSS to a large disk cache that is shared by multiple HENP analysis programs. The system design involved multiple components developed by different people at different sites, and the modules could potentially be distributed as well. We describe the architecture and implementation of the system STACS, emphasizing the inter-module communication requirements. We describe the use of CORBA interfaces between system components, and our experience with using multi-threaded CORBA and moving large objects through the CORBA interfaces. STACS development was recently completed and is being incorporated in an operational environment scheduled to go online in the summer of 1999.